The typical clutch serves as a coupling between two machine components which at times must rotate in unison and at other times must be disconnected so that the one component may rotate while the other remains at rest. Of course, when the clutch is engaged and the two components rotate in unison, torque transfers from the driving component to the driven component. In most applications a clutch must engage gradually to avoid imparting mechanical shocks to the equipment of which it is a part.
Clutches come in a variety of designs and configurations and find widespread use in automotive and industrial equipment. A good clutch should have minimal drag torque, both when engaged and disengaged, should be relatively insensitive to centrifugal and centripetal forces, should be capable of engaging and disengaging at varying speeds and speed differentials, should transmit torque bidirectionally, that is in both directions of rotation, should have low backlash, should damp vibrations, and should protect against overload.
Many clutches of current manufacture require complex actuating mechanisms to engage and disengage them. These mechanisms increase the weight and size of such clutches, not to speak of complexity. Indeed, these clutches typically rely on complex linkages to operate them, and this adversely affects the responsiveness of the clutches and their capacity of to modulate the transfer of torque between rotating components.